Created between 2009 and 2016, Blue Hour is a collection of images that were shot either right before sunrise, or just after sunset, a time period when the sun is below the horizon and the indirect sunlight immerses everything in a predominantly blue shade, also known as the blue hour.

On a photo excursion in New York City in August 2009, Gong walked by Grand Central Terminal and thought the contrast between the classic Mercury Statue Clock atop of the terminal building and the modern glass facade of the skyscraper in the background would make a striking picture. However, the concrete statue and the silver glass looked entirely gray in the viewfinder at the twilight hour. Just as he was about to walk away, the blue hour began working its magic. The glass skyscraper suddenly appeared to be painted in a rich royal blue, and the statue clock was lit up in a glorious golden color.

An image taken during that magic moment, titled Time Goes By, marked the beginning of the series Blue Hour.

The Series was featured in The Christian Science Monitor Weekly Magazine, and on Lost At E Minor.